This is a note to let you know that I've just added the patch titled

    mptcp: pm: avoid possible UaF when selecting endp

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     mptcp-pm-avoid-possible-uaf-when-selecting-endp.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


From stable+bounces-73735-greg=kroah.com@vger.kernel.org Fri Sep  6 10:32:28 2024
From: "Matthieu Baerts (NGI0)" <matttbe@kernel.org>
Date: Fri,  6 Sep 2024 10:31:53 +0200
Subject: mptcp: pm: avoid possible UaF when selecting endp
To: stable@vger.kernel.org, gregkh@linuxfoundation.org
Cc: MPTCP Upstream <mptcp@lists.linux.dev>, "Matthieu Baerts (NGI0)" <matttbe@kernel.org>, Paolo Abeni <pabeni@redhat.com>, Mat Martineau <martineau@kernel.org>, Jakub Kicinski <kuba@kernel.org>
Message-ID: <20240906083151.1768557-4-matttbe@kernel.org>

From: "Matthieu Baerts (NGI0)" <matttbe@kernel.org>

commit 48e50dcbcbaaf713d82bf2da5c16aeced94ad07d upstream.

select_local_address() and select_signal_address() both select an
endpoint entry from the list inside an RCU protected section, but return
a reference to it, to be read later on. If the entry is dereferenced
after the RCU unlock, reading info could cause a Use-after-Free.

A simple solution is to copy the required info while inside the RCU
protected section to avoid any risk of UaF later. The address ID might
need to be modified later to handle the ID0 case later, so a copy seems
OK to deal with.

Reported-by: Paolo Abeni <pabeni@redhat.com>
Closes: https://lore.kernel.org/45cd30d3-7710-491c-ae4d-a1368c00beb1@redhat.com
Fixes: 01cacb00b35c ("mptcp: add netlink-based PM")
Cc: stable@vger.kernel.org
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20240819-net-mptcp-pm-reusing-id-v1-14-38035d40de5b@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
[ Conflicts in pm_netlink.c, because quite a bit of new code has been
  added around since commit 86e39e04482b ("mptcp: keep track of local
  endpoint still available for each msk"). But the issue is still there.
  The conflicts have been resolved using the same way: by adding a new
  parameter to select_local_address() and select_signal_address(), and
  use it instead of the pointer they were previously returning. The code
  is simpler in this version, this conflict resolution looks safe. ]
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/mptcp/pm_netlink.c |   47 ++++++++++++++++++++++++++---------------------
 1 file changed, 26 insertions(+), 21 deletions(-)

--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -158,12 +158,14 @@ static bool lookup_subflow_by_daddr(cons
 	return false;
 }
 
-static struct mptcp_pm_addr_entry *
+static bool
 select_local_address(const struct pm_nl_pernet *pernet,
-		     struct mptcp_sock *msk)
+		     struct mptcp_sock *msk,
+		     struct mptcp_pm_addr_entry *new_entry)
 {
 	const struct sock *sk = (const struct sock *)msk;
-	struct mptcp_pm_addr_entry *entry, *ret = NULL;
+	struct mptcp_pm_addr_entry *entry;
+	bool found = false;
 
 	msk_owned_by_me(msk);
 
@@ -187,18 +189,22 @@ select_local_address(const struct pm_nl_
 		 * pending join
 		 */
 		if (!lookup_subflow_by_saddr(&msk->conn_list, &entry->addr)) {
-			ret = entry;
+			*new_entry = *entry;
+			found = true;
 			break;
 		}
 	}
 	rcu_read_unlock();
-	return ret;
+
+	return found;
 }
 
-static struct mptcp_pm_addr_entry *
-select_signal_address(struct pm_nl_pernet *pernet, unsigned int pos)
+static bool
+select_signal_address(struct pm_nl_pernet *pernet, unsigned int pos,
+		      struct mptcp_pm_addr_entry *new_entry)
 {
-	struct mptcp_pm_addr_entry *entry, *ret = NULL;
+	struct mptcp_pm_addr_entry *entry;
+	bool found = false;
 	int i = 0;
 
 	rcu_read_lock();
@@ -211,12 +217,14 @@ select_signal_address(struct pm_nl_perne
 		if (!(entry->flags & MPTCP_PM_ADDR_FLAG_SIGNAL))
 			continue;
 		if (i++ == pos) {
-			ret = entry;
+			*new_entry = *entry;
+			found = true;
 			break;
 		}
 	}
 	rcu_read_unlock();
-	return ret;
+
+	return found;
 }
 
 unsigned int mptcp_pm_get_add_addr_signal_max(const struct mptcp_sock *msk)
@@ -474,7 +482,7 @@ __lookup_addr(struct pm_nl_pernet *perne
 static void mptcp_pm_create_subflow_or_signal_addr(struct mptcp_sock *msk)
 {
 	struct sock *sk = (struct sock *)msk;
-	struct mptcp_pm_addr_entry *local;
+	struct mptcp_pm_addr_entry local;
 	unsigned int add_addr_signal_max;
 	unsigned int local_addr_max;
 	struct pm_nl_pernet *pernet;
@@ -493,13 +501,11 @@ static void mptcp_pm_create_subflow_or_s
 
 	/* check first for announce */
 	if (msk->pm.add_addr_signaled < add_addr_signal_max) {
-		local = select_signal_address(pernet,
-					      msk->pm.add_addr_signaled);
-
-		if (local) {
-			if (mptcp_pm_alloc_anno_list(msk, local)) {
+		if (select_signal_address(pernet, msk->pm.add_addr_signaled,
+					  &local)) {
+			if (mptcp_pm_alloc_anno_list(msk, &local)) {
 				msk->pm.add_addr_signaled++;
-				mptcp_pm_announce_addr(msk, &local->addr, false);
+				mptcp_pm_announce_addr(msk, &local.addr, false);
 				mptcp_pm_nl_addr_send_ack(msk);
 			}
 		} else {
@@ -514,9 +520,8 @@ static void mptcp_pm_create_subflow_or_s
 	if (msk->pm.local_addr_used < local_addr_max &&
 	    msk->pm.subflows < subflows_max &&
 	    !READ_ONCE(msk->pm.remote_deny_join_id0)) {
-		local = select_local_address(pernet, msk);
-		if (local) {
-			bool fullmesh = !!(local->flags & MPTCP_PM_ADDR_FLAG_FULLMESH);
+		if (select_local_address(pernet, msk, &local)) {
+			bool fullmesh = !!(local.flags & MPTCP_PM_ADDR_FLAG_FULLMESH);
 			struct mptcp_addr_info addrs[MPTCP_PM_ADDR_MAX];
 			int i, nr;
 
@@ -525,7 +530,7 @@ static void mptcp_pm_create_subflow_or_s
 			nr = fill_remote_addresses_vec(msk, fullmesh, addrs);
 			spin_unlock_bh(&msk->pm.lock);
 			for (i = 0; i < nr; i++)
-				__mptcp_subflow_connect(sk, &local->addr, &addrs[i]);
+				__mptcp_subflow_connect(sk, &local.addr, &addrs[i]);
 			spin_lock_bh(&msk->pm.lock);
 			return;
 		}


Patches currently in stable-queue which might be from matttbe@kernel.org are

queue-5.15/mptcp-pm-avoid-possible-uaf-when-selecting-endp.patch
queue-5.15/mptcp-pm-only-decrement-add_addr_accepted-for-mpj-req.patch
queue-5.15/mptcp-pm-fullmesh-select-the-right-id-later.patch
queue-5.15/mptcp-pm-skip-connecting-to-already-established-sf.patch
queue-5.15/mptcp-pm-re-using-id-of-unused-flushed-subflows.patch
queue-5.15/mptcp-pm-add_addr-0-is-not-a-new-address.patch
queue-5.15/mptcp-constify-a-bunch-of-of-helpers.patch
queue-5.15/mptcp-pm-do-not-remove-already-closed-subflows.patch
queue-5.15/mptcp-pr_debug-add-missing-n-at-the-end.patch
queue-5.15/mptcp-pm-check-add_addr_accept_max-before-accepting-new-add_addr.patch
queue-5.15/mptcp-close-subflow-when-receiving-tcp-fin.patch
queue-5.15/mptcp-avoid-duplicated-sub_closed-events.patch
queue-5.15/mptcp-pm-send-ack-on-an-active-subflow.patch